Genomic acquisition of a capsular polysaccharide virulence cluster by non-pathogenic Burkholderia isolates

Bernice Meng Qi Sim, Narisara Chantratita, Wen Fong Ooi, Tannistha Nandi, Ryan Tewhey, Vanaporn Wuthiekanun, Janjira Thaipadungpanit, Sarinna Tumapa, Pramila Ariyaratne, Wing Kin Sung, Xiao Hui Sem, Hui Hoon Chua, Kalpana Ramnarayanan, Chi Ho Lin, Yichun Liu, Edward J. Feil, Mindy B. Glass, Gladys Tan, Sharon J. Peacock, Patrick Tan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Citations (Scopus)

Abstract

Background: Burkholderia thailandensis is a non-pathogenic environmental saprophyte closely related to Burkholderia pseudomallei, the causative agent of the often fatal animal and human disease melioidosis. To study B. thailandensis genomic variation, we profiled 50 isolates using a pan-genome microarray comprising genomic elements from 28 Burkholderia strains and species. Results: Of 39 genomic regions variably present across the B. thailandensis strains, 13 regions corresponded to known genomic islands, while 26 regions were novel. Variant B. thailandensis isolates exhibited isolated acquisition of a capsular polysaccharide biosynthesis gene cluster (B. pseudomallei-like capsular polysaccharide) closely resembling a similar cluster in B. pseudomallei that is essential for virulence in mammals; presence of this cluster was confirmed by whole genome sequencing of a representative variant strain (B. thailandensis E555). Both wholegenome microarray and multi-locus sequence typing analysis revealed that the variant strains formed part of a phylogenetic subgroup distinct from the ancestral B. thailandensis population and were associated with atypical isolation sources when compared to the majority of previously described B. thailandensis strains. In functional assays, B. thailandensis E555 exhibited several B. pseudomallei-like phenotypes, including colony wrinkling, resistance to human complement binding, and intracellular macrophage survival. However, in murine infection assays, B. thailandensis E555 did not exhibit enhanced virulence relative to other B. thailandensis strains, suggesting that additional factors are required to successfully colonize and infect mammals. Conclusions: The discovery of such novel variant strains demonstrates how unbiased genomic surveys of nonpathogenic isolates can reveal insights into the development and emergence of new pathogenic species.

Original languageEnglish
Article numberR89
JournalGenome Biology
Volume11
Issue number1
DOIs
Publication statusPublished - 27 Aug 2010
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported both by core grants from GIS and DMERI and A-star/DSTA grant 08/1/50/19/591. NC, VW, JT, ST and SP were funded by the Wellcome Trust. RT was supported by an East Asia and Pacific Summer Institute grant from the National Science Foundation (USA) and the National Research Foundation (Singapore). We acknowledge the contribution of the GIS community sequencing team in generating the BtE555 genome sequence, in particular Chia-lin Wei and Herve Thoreau.

Publisher Copyright:
© 2006 Sim et al.

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